Renal flare in class V lupus nephritis: increased risk in patients with tubulointerstitial lesions.

The objective of this study is to investigate the risk factors of renal flare in patients with membranous lupus nephritis (class V lupus nephritis). Biopsy-proven pure membranous lupus nephritis patients diagnosed between January 1997 and September 2017 were studied. We assessed and compared the clinical and pathological parameters between patients who experienced renal flare and those who did not. To identify risk factors of renal flare, multivariable Cox proportional hazard regression analysis was performed. Out of the 53 patients with pure membranous lupus nephritis, 17 patients (32.1%) experienced renal flare during a median follow-up of 121.5 months (range 44.4-196.9). Patients who experienced renal flare had significantly higher proportion of tubulointerstitial inflammation (76.5% vs. 36.1%, p = 0.006) and tubular atrophy/interstitial fibrosis (70.6% vs. 27.8%, p = 0.003) at baseline. In multivariable Cox proportional hazard regression analysis, the presence of tubulointerstitial inflammation [adjusted hazard ratio (HR) 5.532, 95% confidence interval (CI) 1.722-17.776, p = 0.004] and tubular atrophy/interstitial fibrosis (adjusted HR 4.328, 95% CI 1.450-12.916, p = 0.009) at baseline was significantly associated with increased risk of renal flare. The presence of tubulointerstitial inflammation and tubular atrophy/interstitial fibrosis is associated with increased risk of renal flare in patients with membranous lupus nephritis.